Generally an thin film electroluminescent display device has a structure wherein a insulating layer is formed on both sides of a fluorescent layer so as to induce a high electrical field around the fluorescent layer when a certain voltage is loaded on both sides of the fluorescent layer. In a conventional structure of a displaying device of thin film electroluminescence as shown in FIG. 1, a transparent substrate 1 laminates a transparent electrode 2, a first insulating layer 3, a fluorescent layer 4, and a second insulating layer 5 sequentially on itself, and a rear electrode 6 is formed on the second insulating layer 5 at regular intervals.
The transparent electrode 2 and the rear electrode 6 are arrayed in a form of a matrix by line etching at regular intervals and the displaying device of the thin film electroluminescence works by an On/Off switch at cross points of the matrix selectively. A strong electrical field is induced by loading an alternative voltage between the transparent electrode 2 and the rear electrode 6, which makes the electrons of shallow level or deep level of an interfaced surface between the insulating layer 3 or 5 and the fluorescent layer 4 to be accelerated toward an opposite polarity, wherein the accelerated electrons strike Mn.sup.2+ of the fluorescent layer 4 composed of zinc sulfide ZnS and Manganese Mn. After being struck, an electron in valence band of the Mn.sup.2+ excited to the conduction state, is returned to the valence band, and then a light with a specific wavelength of 585 nm is radiated from the fluorescent layer.
By selectively applying a voltage on the transparent electrode 2 and the rear electrode 6, the light radiates to the transparent substrate 1 and the rear electrode 6, and the light directed to the rear electrode 6 is reflected and sent to the transparent substrate 1.
Accordingly an image is formed on the displaying device of the thin film electroluminescence by the principle described above.
However, in a conventional device of electroluminescence shown in FIG. 1, it is unable to prevent a light reflected on the rear electrode of which light received from the displaying device and the fluorescent layer because the fluorescent layer 4 has not a light absorbing layer on its rear side. Therefore the performance of the displaying device is deteriorated because a contrast among pixels being on and off becomes poor.
In another conventional device of electroluminescence shown in FIG. 2, a light absorbing layer 7 made of SiNx is introduced to eliminate the above mentioned problem. And the dielectric condition of the light absorbing layer 7 is to have a specific resistance of more than 10.sup.6 .OMEGA.cm. However it is unable to manufacture the layer 7 of SiNx having light absorbing capacity of more than 80% and specific resistance of more than 10.sup.5 .OMEGA.cm by changing the value of `x` of SiNx. Accordingly the specific resistance being less than 10.sup.5 .OMEGA.cm, the adjacent pixels interfere with one another by leaking electrical current. And the layer of SiNx which is not close fitting reduces the life of the device of thin film electroluminescence.